NH3Equilibria
Ammonia gas-aqueous dissolution and dissociation equilibria with van't Hoff temperature dependence. Migrated from Aerosol.jl@c8c640bb src/aqueous_equilibria.jl:345 (`NH3Equilibria` @component). Implements Seinfeld & Pandis Ch 7 §7.3.4 (Eq 7.46–7.51) and Table 7.4. Parameterized as observed-only: T, H_plus, and p_NH3 are inputs; H_NH3, K_a1, K_w, OH_minus, NH3_aq, NH4_plus, NH3_total, H_NH3_eff are algebraic outputs.
Description
Ammonia gas-aqueous dissolution and dissociation equilibria with van’t Hoff temperature dependence. Migrated from Aerosol.jl@c8c640bb src/aqueous_equilibria.jl:345 (NH3Equilibria @component). Implements Seinfeld & Pandis Ch 7 §7.3.4 (Eq 7.46–7.51) and Table 7.4. Parameterized as observed-only: T, H_plus, and p_NH3 are inputs; H_NH3, K_a1, K_w, OH_minus, NH3_aq, NH4_plus, NH3_total, H_NH3_eff are algebraic outputs.
Reference
_source_ref: Aerosol.jl@c8c640bb:src/aqueous_equilibria.jl:345
Upstream NH3Equilibria is an MTK @component where T, H_plus, and p_NH3 are @variables driven by a parent AqueousEquilibria system. For standalone serialization (and to make the component well-posed in isolation), T, H_plus, and p_NH3 are declared as parameters here — matching the bead’s (S, observed-only) classification. The eight algebraic equations are unchanged from upstream.
Tolerance rationale (model-level rel=1e-6): observed-only algebraic system (no ODE integration); 1e-6 covers float64 roundoff in the chained exp/multiplications of the van’t Hoff K(T) and Henry/dissociation closed-form expressions across the atmospheric T range (273–318 K) and 9-decade [H+] sweep._
Parameters
| Name | Units | Default | Description |
|---|---|---|---|
T | K | 298.0 | Temperature |
H_plus | mol/m^3 | 0.0001 | Hydrogen ion concentration (1e-4 mol/m³ = pH 7 in pure water at 298 K) |
p_NH3 | Pa | 1.0 | Partial pressure of NH3 |
R_gas | J/mol/K | 8.314 | Gas constant |
T_ref | K | 298.0 | Reference temperature |
H_NH3_298 | mol/m^3/Pa | 0.611892425363928 | Henry’s law constant for NH3 at 298 K (62.0 M/atm converted to mol/m³/Pa: 62.0 / 101325.0 * 1000.0) |
dH_H_NH3 | J/mol | -34183.28 | Heat of dissolution for NH3 (-8.17 kcal/mol converted to J/mol; Seinfeld & Pandis Table 7.4) |
K_a1_298 | mol/m^3 | 0.017 | NH3.H2O dissociation constant at 298 K (1.7e-5 M converted to mol/m³) |
dH_Ka1 | J/mol | 36191.6 | Enthalpy for K_a1 (8.65 kcal/mol converted to J/mol; Seinfeld & Pandis Table 7.4) |
K_w_298 | mol^2/m^6 | 1e-08 | K_w at 298 K (1.0e-14 M² converted to mol²/m⁶) |
dH_Kw | J/mol | 55856.4 | Enthalpy for K_w (13.35 kcal/mol converted to J/mol; Seinfeld & Pandis Table 7.4) |
Observed
| Name | Units | Default | Description |
|---|---|---|---|
H_NH3 | mol/m^3/Pa | Henry’s law constant for NH3 at temperature T | |
K_a1 | mol/m^3 | NH3.H2O dissociation constant at temperature T | |
K_w | mol^2/m^6 | Water dissociation constant at temperature T | |
OH_minus | mol/m^3 | Hydroxide ion concentration | |
NH3_aq | mol/m^3 | Aqueous NH3 concentration [NH3.H2O] | |
NH4_plus | mol/m^3 | Ammonium ion concentration | |
NH3_total | mol/m^3 | Total dissolved ammonia [NH3.H2O] + [NH4+] | |
H_NH3_eff | mol/m^3/Pa | Effective Henry’s law constant for NH3 (accounts for dissociation) |
Observed expressions
$$ H_{NH3} = H_{NH3\,298} \cdot e^{\frac{dH_{H\,NH3}}{R_{gas}} \cdot \left(\frac{1}{T_{ref}} + \frac{-1}{T}\right)} $$Henry’s law constant for NH3 at temperature T
$$ K_{a1} = K_{a1\,298} \cdot e^{\left(-1\right) \cdot \frac{dH_{Ka1}}{R_{gas}} \cdot \left(\frac{1}{T} + \frac{-1}{T_{ref}}\right)} $$NH3.H2O dissociation constant at temperature T
$$ K_{w} = K_{w\,298} \cdot e^{\left(-1\right) \cdot \frac{dH_{Kw}}{R_{gas}} \cdot \left(\frac{1}{T} + \frac{-1}{T_{ref}}\right)} $$Water dissociation constant at temperature T
$$ OH_{minus} = \frac{K_{w}}{H_{plus}} $$Hydroxide ion concentration
$$ NH3_{aq} = H_{NH3} \cdot p_{NH3} $$Aqueous NH3 concentration [NH3.H2O]
$$ NH4_{plus} = \frac{K_{a1} \cdot NH3_{aq}}{OH_{minus}} $$Ammonium ion concentration
$$ NH3_{total} = NH3_{aq} + NH4_{plus} $$Total dissolved ammonia [NH3.H2O] + [NH4+]
$$ H_{NH3\,eff} = H_{NH3} \cdot \left(1 + \frac{K_{a1} \cdot H_{plus}}{K_{w}}\right) $$Effective Henry’s law constant for NH3 (accounts for dissociation)
Analyses
H_NH3_eff_vs_pH
Effective Henry’s law constant H*_NH3 = H_NH3 * (1 + K_a1*[H+]/K_w) as a function of [H+] over the atmospheric pH range at 298 K. Demonstrates the steep enhancement at low pH (NH4+ partition) and the asymptotic approach to H_NH3 at high pH (NH3.H2O partition) — Seinfeld & Pandis Eq 7.51 / 7.52.
Time span: 0.0 → 1.0
Swept over: H_plus
H_NH3_vs_temperature
NH3 Henry’s law constant vs temperature (van’t Hoff with negative ΔH_dissolution). Reproduces the canonical NH3 solubility curve (Seinfeld & Pandis Table 7.4 row for NH3): H_NH3 climbs from ~0.36 mol/m³/Pa at 310 K to ~2.1 mol/m³/Pa at 273 K — a ~6× range over the atmospheric temperature range.
Time span: 0.0 → 1.0
Swept over: T
coupled_T_pH_sweep
Two-dimensional sweep over T (freezing-to-warm cloud range) and [H+] (acidic-to-basic). Surfaces the joint dependence of [NH4+] and H*_NH3 on temperature and acidity that controls atmospheric NH3 partitioning.
Time span: 0.0 → 1.0
Swept over: T, H_plus
Raw .esm
Raw .esm JSON (this component)
{
"reference": {
"notes": "source_ref: Aerosol.jl@c8c640bb:src/aqueous_equilibria.jl:345\nUpstream `NH3Equilibria` is an MTK `@component` where T, H_plus, and p_NH3 are `@variables` driven by a parent `AqueousEquilibria` system. For standalone serialization (and to make the component well-posed in isolation), T, H_plus, and p_NH3 are declared as parameters here — matching the bead's `(S, observed-only)` classification. The eight algebraic equations are unchanged from upstream.\n\nTolerance rationale (model-level rel=1e-6): observed-only algebraic system (no ODE integration); 1e-6 covers float64 roundoff in the chained exp/multiplications of the van't Hoff K(T) and Henry/dissociation closed-form expressions across the atmospheric T range (273–318 K) and 9-decade [H+] sweep."
},
"tolerance": {
"rel": 1e-06
},
"variables": {
"T": {
"type": "parameter",
"units": "K",
"default": 298.0,
"description": "Temperature"
},
"H_plus": {
"type": "parameter",
"units": "mol/m^3",
"default": 0.0001,
"description": "Hydrogen ion concentration (1e-4 mol/m³ = pH 7 in pure water at 298 K)"
},
"p_NH3": {
"type": "parameter",
"units": "Pa",
"default": 1.0,
"description": "Partial pressure of NH3"
},
"R_gas": {
"type": "parameter",
"units": "J/mol/K",
"default": 8.314,
"description": "Gas constant"
},
"T_ref": {
"type": "parameter",
"units": "K",
"default": 298.0,
"description": "Reference temperature"
},
"H_NH3_298": {
"type": "parameter",
"units": "mol/m^3/Pa",
"default": 0.611892425363928,
"description": "Henry's law constant for NH3 at 298 K (62.0 M/atm converted to mol/m³/Pa: 62.0 / 101325.0 * 1000.0)"
},
"dH_H_NH3": {
"type": "parameter",
"units": "J/mol",
"default": -34183.28,
"description": "Heat of dissolution for NH3 (-8.17 kcal/mol converted to J/mol; Seinfeld & Pandis Table 7.4)"
},
"K_a1_298": {
"type": "parameter",
"units": "mol/m^3",
"default": 0.017,
"description": "NH3.H2O dissociation constant at 298 K (1.7e-5 M converted to mol/m³)"
},
"dH_Ka1": {
"type": "parameter",
"units": "J/mol",
"default": 36191.6,
"description": "Enthalpy for K_a1 (8.65 kcal/mol converted to J/mol; Seinfeld & Pandis Table 7.4)"
},
"K_w_298": {
"type": "parameter",
"units": "mol^2/m^6",
"default": 1e-08,
"description": "K_w at 298 K (1.0e-14 M² converted to mol²/m⁶)"
},
"dH_Kw": {
"type": "parameter",
"units": "J/mol",
"default": 55856.4,
"description": "Enthalpy for K_w (13.35 kcal/mol converted to J/mol; Seinfeld & Pandis Table 7.4)"
},
"H_NH3": {
"type": "unknown",
"units": "mol/m^3/Pa",
"description": "Henry's law constant for NH3 at temperature T"
},
"K_a1": {
"type": "unknown",
"units": "mol/m^3",
"description": "NH3.H2O dissociation constant at temperature T"
},
"K_w": {
"type": "unknown",
"units": "mol^2/m^6",
"description": "Water dissociation constant at temperature T"
},
"OH_minus": {
"type": "unknown",
"units": "mol/m^3",
"description": "Hydroxide ion concentration"
},
"NH3_aq": {
"type": "unknown",
"units": "mol/m^3",
"description": "Aqueous NH3 concentration [NH3.H2O]"
},
"NH4_plus": {
"type": "unknown",
"units": "mol/m^3",
"description": "Ammonium ion concentration"
},
"NH3_total": {
"type": "unknown",
"units": "mol/m^3",
"description": "Total dissolved ammonia [NH3.H2O] + [NH4+]"
},
"H_NH3_eff": {
"type": "unknown",
"units": "mol/m^3/Pa",
"description": "Effective Henry's law constant for NH3 (accounts for dissociation)"
}
},
"equations": [
{
"lhs": "H_NH3",
"rhs": {
"op": "*",
"args": [
"H_NH3_298",
{
"op": "exp",
"args": [
{
"op": "*",
"args": [
{
"op": "/",
"args": [
"dH_H_NH3",
"R_gas"
]
},
{
"op": "+",
"args": [
{
"op": "/",
"args": [
1,
"T_ref"
]
},
{
"op": "/",
"args": [
-1,
"T"
]
}
]
}
]
}
]
}
]
}
},
{
"lhs": "K_a1",
"rhs": {
"op": "*",
"args": [
"K_a1_298",
{
"op": "exp",
"args": [
{
"op": "*",
"args": [
-1,
{
"op": "/",
"args": [
"dH_Ka1",
"R_gas"
]
},
{
"op": "+",
"args": [
{
"op": "/",
"args": [
1,
"T"
]
},
{
"op": "/",
"args": [
-1,
"T_ref"
]
}
]
}
]
}
]
}
]
}
},
{
"lhs": "K_w",
"rhs": {
"op": "*",
"args": [
"K_w_298",
{
"op": "exp",
"args": [
{
"op": "*",
"args": [
-1,
{
"op": "/",
"args": [
"dH_Kw",
"R_gas"
]
},
{
"op": "+",
"args": [
{
"op": "/",
"args": [
1,
"T"
]
},
{
"op": "/",
"args": [
-1,
"T_ref"
]
}
]
}
]
}
]
}
]
}
},
{
"lhs": "OH_minus",
"rhs": {
"op": "/",
"args": [
"K_w",
"H_plus"
]
}
},
{
"lhs": "NH3_aq",
"rhs": {
"op": "*",
"args": [
"H_NH3",
"p_NH3"
]
}
},
{
"lhs": "NH4_plus",
"rhs": {
"op": "/",
"args": [
{
"op": "*",
"args": [
"K_a1",
"NH3_aq"
]
},
"OH_minus"
]
}
},
{
"lhs": "NH3_total",
"rhs": {
"op": "+",
"args": [
"NH3_aq",
"NH4_plus"
]
}
},
{
"lhs": "H_NH3_eff",
"rhs": {
"op": "*",
"args": [
"H_NH3",
{
"op": "+",
"args": [
1,
{
"op": "/",
"args": [
{
"op": "*",
"args": [
"K_a1",
"H_plus"
]
},
"K_w"
]
}
]
}
]
}
}
],
"tests": [
{
"id": "baseline_298K_pH7",
"description": "Reference state at 298 K (T_ref) with neutral water (pH 7) and 1 Pa NH3. At T=T_ref the van't Hoff factors are exp(0)=1, so H_NH3, K_a1, K_w take their 298 K values directly. NH4+ dominates over NH3.H2O at pH 7 because K_a1/[OH-] = 0.017/1e-4 = 170.",
"parameter_overrides": {
"T": 298.0,
"H_plus": 0.0001,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "H_NH3",
"time": 0.0,
"expected": 0.611892425363928
},
{
"variable": "K_a1",
"time": 0.0,
"expected": 0.017
},
{
"variable": "K_w",
"time": 0.0,
"expected": 1e-08
},
{
"variable": "OH_minus",
"time": 0.0,
"expected": 9.999999999999999e-05
},
{
"variable": "NH3_aq",
"time": 0.0,
"expected": 0.611892425363928
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 104.02171231186777
},
{
"variable": "NH3_total",
"time": 0.0,
"expected": 104.6336047372317
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 104.63360473723169
}
]
},
{
"id": "cold_273K_pH7",
"description": "Cold cloud-water reference (273.15 K) at pH 7. NH3 solubility increases sharply at low T (negative ΔH_dissolution), so H_NH3 grows ~3.5×; K_w decreases (positive ΔH_dissociation) so [OH-] drops; NH4+ partition increases dramatically.",
"parameter_overrides": {
"T": 273.15,
"H_plus": 0.0001,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "H_NH3",
"time": 0.0,
"expected": 2.1468472319851686
},
{
"variable": "K_a1",
"time": 0.0,
"expected": 0.0045008637550133
},
{
"variable": "K_w",
"time": 0.0,
"expected": 1.2860247646167109e-09
},
{
"variable": "OH_minus",
"time": 0.0,
"expected": 1.2860247646167108e-05
},
{
"variable": "NH3_aq",
"time": 0.0,
"expected": 2.1468472319851686
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 751.3593174757062
},
{
"variable": "NH3_total",
"time": 0.0,
"expected": 753.5061647076914
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 753.5061647076913
}
]
},
{
"id": "cold_280K_pH7",
"description": "Intermediate cold-water reference (280 K).",
"parameter_overrides": {
"T": 280.0,
"H_plus": 0.0001,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "H_NH3",
"time": 0.0,
"expected": 1.485508143572881
},
{
"variable": "K_a1",
"time": 0.0,
"expected": 0.006646880554687791
},
{
"variable": "K_w",
"time": 0.0,
"expected": 2.3473232097928894e-09
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 420.64915270940264
}
]
},
{
"id": "warm_310K_pH7",
"description": "Warm-cloud / body-temperature reference (310 K). NH3 solubility falls (negative ΔH_dissolution), but K_w rises so [OH-] increases and NH4+ partition decreases.",
"parameter_overrides": {
"T": 310.0,
"H_plus": 0.0001,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "H_NH3",
"time": 0.0,
"expected": 0.3586961490688435
},
{
"variable": "K_a1",
"time": 0.0,
"expected": 0.029924341719995504
},
{
"variable": "K_w",
"time": 0.0,
"expected": 2.3933701536339305e-08
},
{
"variable": "OH_minus",
"time": 0.0,
"expected": 0.00023933701536339304
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 44.847831506903056
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 45.206527655971904
}
]
},
{
"id": "hot_318K_pH7",
"description": "Upper-range reference (318 K, 45 °C) for warm aqueous-phase chemistry.",
"parameter_overrides": {
"T": 318.0,
"H_plus": 0.0001,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "H_NH3",
"time": 0.0,
"expected": 0.25693293054745164
},
{
"variable": "K_a1",
"time": 0.0,
"expected": 0.042603477905336945
},
{
"variable": "K_w",
"time": 0.0,
"expected": 4.128494581583288e-08
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 26.5138689501051
}
]
},
{
"id": "acidic_pH4_298K",
"description": "Acidic cloud water (pH 4, typical polluted rain) at 298 K. Low [OH-] drives NH4+ to dominate by 5 orders of magnitude over NH3.H2O — equivalently H*_NH3 grows by K_a1*[H+]/K_w = 0.017*0.1/1e-8 ≈ 1.7e5.",
"parameter_overrides": {
"T": 298.0,
"H_plus": 0.1,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "OH_minus",
"time": 0.0,
"expected": 1e-07
},
{
"variable": "NH3_aq",
"time": 0.0,
"expected": 0.611892425363928
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 104021.71231186777
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 104022.32420429312
}
]
},
{
"id": "acidic_pH2_298K",
"description": "Strongly acidic regime (pH 2, [H+] = 10 mol/m³) at 298 K. Stress-tests the [H+]/K_w ratio in H_NH3_eff at the far-acidic tail where dissociation overwhelmingly favors NH4+.",
"parameter_overrides": {
"T": 298.0,
"H_plus": 10.0,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "OH_minus",
"time": 0.0,
"expected": 1e-09
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 10402171.231186775
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 10402171.8430792
}
]
},
{
"id": "basic_pH9_298K",
"description": "Mildly basic regime (pH 9) at 298 K. Higher [OH-] suppresses NH4+ partition; NH3.H2O contribution to total becomes non-negligible (~37 %).",
"parameter_overrides": {
"T": 298.0,
"H_plus": 1e-06,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "OH_minus",
"time": 0.0,
"expected": 0.01
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 1.0402171231186776
},
{
"variable": "NH3_total",
"time": 0.0,
"expected": 1.6521095484826056
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 1.6521095484826056
}
]
},
{
"id": "basic_pH10_298K",
"description": "Basic regime (pH 10) at 298 K. NH3.H2O begins to dominate over NH4+ (NH3_aq/NH4+ = OH-/K_a1 ≈ 0.1/0.017 ≈ 5.9).",
"parameter_overrides": {
"T": 298.0,
"H_plus": 1e-07,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "OH_minus",
"time": 0.0,
"expected": 0.1
},
{
"variable": "NH3_aq",
"time": 0.0,
"expected": 0.611892425363928
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 0.10402171231186776
},
{
"variable": "NH3_total",
"time": 0.0,
"expected": 0.7159141376757957
}
]
},
{
"id": "high_pNH3",
"description": "Henry's-law linearity check: 10× p_NH3 at fixed T, H_plus scales NH3_aq, NH4+, NH3_total by 10× while leaving H_NH3, K_a1, K_w, OH-, H_NH3_eff unchanged.",
"parameter_overrides": {
"T": 298.0,
"H_plus": 0.0001,
"p_NH3": 10.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "NH3_aq",
"time": 0.0,
"expected": 6.11892425363928
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 1040.2171231186778
},
{
"variable": "NH3_total",
"time": 0.0,
"expected": 1046.3360473723171
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 104.63360473723169
}
]
},
{
"id": "low_pNH3",
"description": "Henry's-law linearity check at low partial pressure: p_NH3 = 0.01 Pa scales NH3_aq, NH4+, NH3_total by 0.01× from baseline. H_NH3_eff is independent of p_NH3.",
"parameter_overrides": {
"T": 298.0,
"H_plus": 0.0001,
"p_NH3": 0.01
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "NH3_aq",
"time": 0.0,
"expected": 0.00611892425363928
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 1.0402171231186779
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 104.63360473723169
}
]
},
{
"id": "coupled_cold_acidic",
"description": "Cross-check: cold (273.15 K) AND acidic (pH 4). Combines the van't Hoff temperature shift with the acidic [H+] sweep to exercise both coefficient paths at once.",
"parameter_overrides": {
"T": 273.15,
"H_plus": 0.1,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "H_NH3",
"time": 0.0,
"expected": 2.1468472319851686
},
{
"variable": "K_w",
"time": 0.0,
"expected": 1.2860247646167109e-09
},
{
"variable": "OH_minus",
"time": 0.0,
"expected": 1.2860247646167107e-08
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 751359.3174757062
},
{
"variable": "H_NH3_eff",
"time": 0.0,
"expected": 751361.4643229382
}
]
},
{
"id": "coupled_warm_basic",
"description": "Cross-check: warm (310 K) AND basic (pH 9). Higher T and higher pH together push the system toward NH3.H2O-dominated speciation.",
"parameter_overrides": {
"T": 310.0,
"H_plus": 1e-06,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"assertions": [
{
"variable": "H_NH3",
"time": 0.0,
"expected": 0.3586961490688435
},
{
"variable": "OH_minus",
"time": 0.0,
"expected": 0.023933701536339308
},
{
"variable": "NH3_aq",
"time": 0.0,
"expected": 0.3586961490688435
},
{
"variable": "NH4_plus",
"time": 0.0,
"expected": 0.4484783150690305
},
{
"variable": "NH3_total",
"time": 0.0,
"expected": 0.807174464137874
}
]
}
],
"analyses": [
{
"id": "H_NH3_eff_vs_pH",
"description": "Effective Henry's law constant H*_NH3 = H_NH3 * (1 + K_a1*[H+]/K_w) as a function of [H+] over the atmospheric pH range at 298 K. Demonstrates the steep enhancement at low pH (NH4+ partition) and the asymptotic approach to H_NH3 at high pH (NH3.H2O partition) — Seinfeld & Pandis Eq 7.51 / 7.52.",
"initial_state": {},
"parameters": {
"T": 298.0,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"parameter_sweep": {
"type": "cartesian",
"dimensions": [
{
"parameter": "H_plus",
"range": {
"start": 1e-07,
"stop": 10.0,
"count": 25,
"scale": "log"
}
}
]
},
"plots": [
{
"id": "Hstar_curve",
"type": "line",
"description": "H*_NH3 vs [H+] at 298 K — log-log slope ≈ -1 in the acidic regime (K_a1*[H+]/K_w >> 1).",
"x": {
"variable": "H_plus",
"label": "[H⁺] (mol/m³, log scale)"
},
"y": {
"variable": "H_NH3_eff",
"label": "H*_NH3 (mol/m³/Pa, log scale)"
}
},
{
"id": "NH4_curve",
"type": "line",
"description": "[NH4+] vs [H+] at fixed p_NH3 = 1 Pa.",
"x": {
"variable": "H_plus",
"label": "[H⁺] (mol/m³, log scale)"
},
"y": {
"variable": "NH4_plus",
"label": "[NH4⁺] (mol/m³, log scale)"
}
}
]
},
{
"id": "H_NH3_vs_temperature",
"description": "NH3 Henry's law constant vs temperature (van't Hoff with negative ΔH_dissolution). Reproduces the canonical NH3 solubility curve (Seinfeld & Pandis Table 7.4 row for NH3): H_NH3 climbs from ~0.36 mol/m³/Pa at 310 K to ~2.1 mol/m³/Pa at 273 K — a ~6× range over the atmospheric temperature range.",
"initial_state": {},
"parameters": {
"H_plus": 0.0001,
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"parameter_sweep": {
"type": "cartesian",
"dimensions": [
{
"parameter": "T",
"range": {
"start": 273.15,
"stop": 318.0,
"count": 20,
"scale": "linear"
}
}
]
},
"plots": [
{
"id": "HNH3_curve",
"type": "line",
"description": "H_NH3(T) — van't Hoff curve.",
"x": {
"variable": "T",
"label": "Temperature (K)"
},
"y": {
"variable": "H_NH3",
"label": "H_NH3 (mol/m³/Pa, log scale)"
}
},
{
"id": "Ka1_curve",
"type": "line",
"description": "K_a1(T) — dissociation constant climbs with T.",
"x": {
"variable": "T",
"label": "Temperature (K)"
},
"y": {
"variable": "K_a1",
"label": "K_a1 (mol/m³, log scale)"
}
}
]
},
{
"id": "coupled_T_pH_sweep",
"description": "Two-dimensional sweep over T (freezing-to-warm cloud range) and [H+] (acidic-to-basic). Surfaces the joint dependence of [NH4+] and H*_NH3 on temperature and acidity that controls atmospheric NH3 partitioning.",
"initial_state": {},
"parameters": {
"p_NH3": 1.0
},
"time_span": {
"start": 0.0,
"end": 1.0
},
"parameter_sweep": {
"type": "cartesian",
"dimensions": [
{
"parameter": "T",
"range": {
"start": 273.15,
"stop": 318.0,
"count": 10,
"scale": "linear"
}
},
{
"parameter": "H_plus",
"range": {
"start": 1e-07,
"stop": 1.0,
"count": 15,
"scale": "log"
}
}
]
},
"plots": [
{
"id": "Hstar_heatmap",
"type": "heatmap",
"description": "H*_NH3 as a function of T and [H+].",
"x": {
"variable": "T",
"label": "Temperature (K)"
},
"y": {
"variable": "H_plus",
"label": "[H⁺] (mol/m³, log scale)"
},
"value": {
"variable": "H_NH3_eff",
"reduce": "final"
}
}
]
}
]
}